The suitability guides in the various animal topics are created by a program. Among other things, this program also checks for a number of common problems and inefficiencies inside the animal's configuration. These are listed at the top of the guides in "Results From Configuration Checking" sections. The messages use terms that are inside Zoo Tycoon's animal configuration files. So they will probably be confusing to most people except for some animal designers.
There are two types of messages that can appear in these sections. The first type is a Warning. The animal will still work if it has Warnings and the problems or inefficiencies will probably not be obvious unless one looks hard for them, if at all. For example, maybe female and young animals will stand around more than male animals. Or maybe the animal has a frown when another of its kind is added. Or maybe an animal is happier if it has some other foliage instead of the one shown as the preferred foliage or if it has foliage from a different habitat than what is shown. Or maybe an animal moves slower when it looks like it is running than when it looks like it is walking. The second type of message is an Error. These are more serious. They could cause game crashes or be very obvious to see. For example, maybe the game will crash when the mouse is moved to the animal in the purchase menu and the ZT version is not an American English version. (In Zoo Tycoon's terms, this is an LCID error.) Or maybe the game will crash when the animal enters or is placed in water terrain. Or maybe the animal will stand on the water terrain instead of swim when it is placed in it.
For more in depth information go Here (http://www.ztcdd.org/DD/index.php?topic=9318.0)